Polycarbonate - Before Trivex lenses were introduced, Polycarbonate lenses were the lightest weight lens available. It is in fact a form of plexi-glass. It blocks UV rays, is shatter resistant and is used in many sports glasses and glasses for children and teenagers. Because polycarbonate is soft and will scratch easily, scratch resistant coatings are included with the lenses. Most optical stores use polycarbonate because they claim it is the most impact resistant, thin, lightweight lens.